The right and left sides of the heart differ structurally to support their distinct roles in circulation. The right side receives deoxygenated blood from the body through the superior and inferior vena cava into the right atrium, which contracts to push blood into the right ventricle. The right ventricle has a thinner, crescent-shaped muscular wall because it only needs to pump blood a short distance to the lungs through the pulmonary artery, where resistance is relatively low.
The left side receives oxygenated blood from the lungs through the pulmonary veins into the left atrium, which then contracts to fill the left ventricle. The left ventricle has a much thicker, conical muscular wall—roughly two to three times thicker than the right ventricle—because it must generate the force needed to pump blood throughout the entire body against high arterial resistance through the aorta.
Both sides contain four chambers total: two atria (receiving chambers) and two ventricles (pumping chambers). However, a thick muscular wall called the interventricular septum separates the left and right ventricles. The atrial walls are thinner than the ventricular walls because atria need only to deliver blood to the ventricles below them, not pump it through distant vessels. Both sides have one-way valves—the tricuspid valve on the right and the mitral valve on the left—that prevent blood from flowing backward during contraction. These structural differences allow each side to perform its specific function efficiently within the pulmonary and systemic circulation.